Tune part 16

[rust-101.git] / workspace / src / part08.rs

diff --git a/workspace/src/part08.rs b/workspace/src/part08.rs
index 5a5f79222071bb9359eee608acee23e37102e6ee..01189060eb1b958256583d0eb1717bcc94319976 100644 (file)
--- a/workspace/src/part08.rs
+++ b/workspace/src/part08.rs
@@ -7,7 +7,7 @@ use part05::BigInt;
 
 // So, let us write a function to "add with carry", and give it the appropriate type. Notice Rust's native support for pairs.
 fn overflowing_add(a: u64, b: u64, carry: bool) -> (u64, bool) {
-    let sum = u64::wrapping_add(a, b);
+    let sum = a.wrapping_add(b);
     // If an overflow happened, then the sum will be smaller than *both* summands. Without an overflow, of course, it will be
     // at least as large as both of them. So, let's just pick one and check.
     if sum >= a {
@@ -15,7 +15,7 @@ fn overflowing_add(a: u64, b: u64, carry: bool) -> (u64, bool) {
         // **Exercise 08.1**: Write the code to handle adding the carry in this case.
         unimplemented!()
     } else {
-        // The addition *did* overflow. It is impossible for the addition of the carry
+        // Otherwise, the addition *did* overflow. It is impossible for the addition of the carry
         // to overflow again, as we are just adding 0 or 1.
         unimplemented!()
     }
@@ -69,21 +69,25 @@ impl<'a, 'b> ops::Add<&'a BigInt> for &'b BigInt {
     }
 }
 
+// **Exercise 08.4**: Implement the two missing combinations of arguments for `Add`. You should not have to duplicate the implementation.
+
 // ## Modules
 
 // Rust calls a bunch of definitions that are grouped together a *module*. You can put the tests in a submodule as follows.
 #[cfg(test)]
 mod tests {
-    #[test]
+    use part05::BigInt;
+
+    /*#[test]*/
     fn test_add() {
         let b1 = BigInt::new(1 << 32);
         let b2 = BigInt::from_vec(vec![0, 1]);
 
         assert_eq!(&b1 + &b2, BigInt::from_vec(vec![1 << 32, 1]));
-        // **Exercise 08.4**: Add some more cases to this test.
+        // **Exercise 08.5**: Add some more cases to this test.
     }
 }
 
-// **Exercise 08.4**: Write a subtraction function, and testcases for it. Decide for yourself how you want to handle negative results.
+// **Exercise 08.6**: Write a subtraction function, and testcases for it. Decide for yourself how you want to handle negative results.
 // For example, you may want to return an `Option`, to panic, or to return `0`.